Hardfacing materials applied to drill stems have been utilized in the oil industry since its origins, which may have been around the late 1930's. The first hardband materials consisted of a mild steel matrix with crushed sintered tungsten carbide particles. These materials performed relatively well for more than half a century as the relatively simple vertical, shallow wells in which they were employed did not put many requirements on the hardfacing materials.
Initially, hardband was designed to protect drill stem elements from rotational wear and to extend their life as casing wear was not an issue for vertical holes. As wells became deeper and deviated with more complicated well designs, an increasing number of casing failures started to become common. Today, the need to reach deeper more remote hydrocarbon reservoirs appears to have pushed the limits of traditional drilling programs. The shallow, easy formations are becoming depleted and focus has begun to turn to deeper, more remote, and challenging reservoirs.
Since the oil industry's beginnings, drill pipe has been used to drill wells and more recently, its material requirements including, mechanical properties, capabilities, and performance, have evolved in response to the evolution of the newer drilling challenges. Maintaining drill pipe integrity is relatively important for both the drilling contractor and the well operator.
Thus, a need to develop casing friendly hardfacing materials that extend the life of the drill pipe while at the same time protecting the casing has been appreciated. For decades the industry has used traditional materials such as tungsten carbide (WC), chrome carbide, and other alloying overlays to improve the abrasion resistance on tool joint components. Typical materials may be good at protecting either the drill pipe or the casing but typically are not understood to protect both. Materials such as tungsten carbide (W) based overlays have performed well in open-hole situations but may dramatically reduce casing life. Chrome carbide overlays may work relatively well in preventing casing wear but provide relatively limited tool joint protection. Other factors that may be considered include, but are not limited to, application, performance and longevity of the hardfacing material.
In addition to relatively improved hardness and wear resistance, it may be appreciated that it would be desirable to make materials that are crack free. Cracks once initiated during welding may potentially cause issues. Some of the perceived worst type of cracks may include those formed in the underbead or longitudinal cracking which can produce overlay failure from chipping and/or spallation. Typical transverse cracks or cross checking cracks may be less problematic and may usually be blunted by the ductile substrate. However, during the lifetime of the tool joint, these cracks may cause some issues when drilling complex drill profiles.
In order to meet various industrial requirements for an advanced hardbanding material, it may be advantageous to reduce the scale of the microstructure of the material. Such reduction may lead to relatively higher hardness and wear resistance in combination with relatively higher toughness and improved crack resistance. The utilization of glass forming chemistries may be beneficial in refining the scale of the crystalline microstructure, especially during welding where high heat input and slow cooling rates may result in the formation of coarse metallurgical structures. The level of refinement may depend on a variety of factors including, for example, the glass forming ability of the alloy, the cooling rate of the industrial processing method, the total heat input, the thickness of the weld overlay deposit, etc. In the relatively extreme case, the average cooling rate of the industrial welding process may be greater (i.e. faster) than the critical cooling rate for metallic glass formation of the feedstock material, and metallic glass weld deposits formed during welding. If the total heat input is insufficient to cause devitrification, metallic glass overlays may be formed with an angstrom scale microstructure, but if the total heat input is too great, then partially or complete devitrification may occur resulting in the formation of a nanoscale composite microstructure.
Alternatively, if the critical cooling rate for metallic glass formation is greater than the average cooling rate of the chosen industrial weld overlay process, high undercoolings may still be obtained prior to nucleation and growth. Undercooling may be understood as the cooling of a liquid below its equilibrium freezing temperature while the material remains liquid. The undercooling, which may be many hundreds of degrees greater than that obtained in conventional alloys, may result in relatively higher driving forces for nucleation and combined with a simultaneous reduction in the temperature dependant diffusional processes, may result in an increased nucleation frequency and reduced time for grain/phase growth. Thus, as the level of undercooling is increased, the resulting average grain/phase size may be reduced. This reduction of both matrix grain/phase sizes and hard particle sizes may result in an increase in weld overlay toughness since relatively less stress concentration may occur in individual particles and any cracks produced in a hard brittle phase may be arrested/bridged in the more ductile matrix phases.